Chronic sleep disturbance is reported by nearly 50% of older adults. Sleep loss also occurs at all ages due to bedtime curtailment, an increasingly prevalent condition. Recent data have revealed the role of sleep duration and quality in metabolic and endocrine function and have indicated that chronic sleep loss may accelerate the development or increase the severity of age-related diseases such as obesity and diabetes. Despite its high prevalence, chronic sleep loss has been understudied. The present Project focuses on the interaction of chronic partial sleep loss and aging. A multi-disciplinary approach combining epidemiology, clinical research (in older insomniacs, middle-aged subjects at risk for obesity and healthy adults of all ages), in vivo studies in laboratory rodents and molecular and genetic analyses will be used to: 1. Delineate the impact of age on sleep regulation during adaptation to and recovery from chronic partial sleep loss; 2. Test the hypothesis that chronic partial sleep loss has adverse effects on biomarkers of aging and increases the risk of obesity and diabetes; 3. Test the hypothesis that paying a sleep debt and/or improving sleep quality has beneficial health and neurobehavioral effects at all stages of adulthood; 4. Determine the influence of the circadian clock on the response to chronic sleep loss; 5. Explore the mechanisms linking chronic sleep loss and metabolic aging; 6. Define the determinants of individual differences in sleep capacity and vulnerability to sleep loss in young adulthood, midlife and late life. Project 6 will determine the role of sleep in weight gain in mid life. Project 7 will examine whether exercise is an effective countermeasure for sleep loss in older insomniacs. Project 8 will delineate the role of sleep duration in metabolic aging and weight gain. Project 9 will determine the impact of a sleep debt and individual sleep capacity in young, middle-aged and older men and women. Project 10 will use rat models to define the impact of age on physiologic adaptation to and recovery from sleep restriction. Project 11 will utilize a genetic model of chronic sleep loss with age-related obesity, the Clock mouse, to explore mechanisms linking circadian function, sleep and metabolism. Core 9001 (Methods and Analysis) will provide monitoring equipment for humans and rodents, methods for quantifying output variables and biostatistical support. Core 9002 (Laboratory) will assay blood, saliva and urine constituents for Projects 7, 8 & 9.